This is mostly two problems spread out far and wide:
- ypldap_process should be declared properly
- debug is defined differently in many programs
For the latter, just extern it and define it everywhere that actually needs
it. This mostly works out nicely for ^/libexec/ypxfr, which can remove the
assignment at the beginning of main in favor of defining it properly.
-fno-common will become the default in GCC10/LLVM11.
MFC after: 3 days
3a166b3323